This invention relates to a fluid-tight drip pan, and more specifically to a fluid-tight drip pan for the engine or transmission compartment of a helicopter.
Helicopters, in general, have the same basic configuration or layout. For instance, a typical helicopter will have a cabin section which is used to transport people, cargo or both. In addition, the helicopter will have an engine compartment which is located typically above and to the rear of the cabin section. The engine compartment will house two primary components, at least one engine and a rotor transmission with a corresponding transmission housing.
Both the engine and the rotor transmission contain numerous fluids, such as petroleum-based lubricants, that are critical to the operation of the engine and the transmission. These fluids inevitably leak from various locations in the engine and the transmission during both the operation and storage of the helicopter. Because the engine compartment is generally oriented above the cabin section, any leaking fluids eventually seep or drip into the cabin section, unless proper sealing mechanisms are in place. The inflow of these leaking fluids spoil, stain or damage the cabin""s interior materials such as seat covers and acoustic linings. In addition, the leaking fluids can severely damage or destroy sensitive electronic equipment that may be placed in the cabin section of, for instance, a Blackhawk(trademark) helicopter.
Moreover, the exterior of the helicopter around the engine and transmission compartment is not completely fluidtight, allowing fluid such as water to leak from these areas into the cabin with similar adverse effects.
During routine inspection and maintenance it is necessary to have ready access to the engine and the rotor transmission. Such access is required to check critical fluid levels, to replace worn or damaged parts, or to adjust mechanical systems. Typically, various access panels in or around the engine compartment provide the requisite openings to achieve ready access to the engine and the rotor transmission. In some helicopters, such as the Blackhawk(trademark) helicopter, a forged airframe structure forms an access opening which is located below the rotor transmission housing and above the cabin section. The opening is thus accessible through the cabin""s ceiling. This access opening, however, must be sealed by a cover against the inevitable oil and fluid drippings which the engine and the rotor transmission will produce, as well as against water leakage.
The access opening below the engine compartment in the Blackhawk(trademark) helicopter is defined by both the aircraft structural forgings and a flexible or yieldable downwardly-turned skirt which is riveted onto the helicopter""s forged structure. The skirt is thin and many times more flexible relative to the helicopter""s forged structure.
Prior drip pan designs attached a covering plate directly to the flexible skirt with a hollow seal sandwiched therebetween. One hollow seal used in prior designs resembled the flexible, hollow door seals used around car doors or refrigerator doors. However, the skirt contains surface aberrations, such as the protruding rivet heads from the rivets securing the skirt to the forged helicopter structure. When the seal engaged both the skirt and the rivet heads, it could be upset enough so that leakage occurred. Accordingly, the hollow seal traversing these aberrations while sandwiched between the skirt and the covering plate is unable to provide a suitable, consistent, long-term fluid seal. Moreover, flexing of the flexible skirt could also cause leakage.
Also, the geometry of the cover cannot be such that it protrudes significantly into the interior of the cabin section. Headroom in the cabin section typically is limited and any additional protrusion from the ceiling of the cabin section is undesirable. In addition, because weight is critical to the operation of any aircraft, heavy cover constructions are undesirable.
The drip pan design disclosed in copending U.S. patent application Ser. No. 09/069,920, filed Apr. 30, 1998, which is fully incorporated herein by reference, provided improvements to prior drip pan designs. However, even this drip pan design can be improved upon further, particularly in the area of the seal and the attachment of the drip pan to its attachment frame.
Accordingly, one objective of this invention is to provide an improved cover and seal for the interior access opening of helicopters such as the Blackhawk(trademark) helicopter and those of similar structure.
Another object of this invention is to provide a drip pan that will effectively and consistently seal fluid from passage from an engine or transmission compartment to a cabin section of a helicopter.
Another object of this invention is to provide a drip pan which permits quick access to the engine or transmission compartment of a helicopter without requiring modification to the existing aircraft structure.
Another objective of the invention is to more effectively seal a drip pan to the skirt defining a transmission access opening in a Blackhawk(trademark) helicopter.
Still another object of this invention is to provide a drip pan that can be attached to the existing structure of a Blackhawk(trademark) helicopter without modification of the existing airframe structure and with minimal intrusion into the helicopter""s cabin section.
These and other objects of the invention are provided for by a helicopter drip pan apparatus which covers and effectively seals a structural opening in the helicopter without leakage. According to one embodiment of the invention, the drip pan apparatus includes a frame member adapted to mount to the structural opening of the helicopter. Unlike prior drip pan designs, the frame member may mount directly to the forged structure of the helicopter or to a flexible skirt required by prior designs. The frame member has an inwardly-facing peripheral surface extending around the frame member. The frame member and thus the surface have at least one linear portion. A drip pan is selectively affixed to the frame member. The drip pan includes an outwardly-facing peripheral groove which extends around the outside edge of the drip pan. Like the surface of the frame member, the groove has at least one linear portion. The perimeter of the drip pan conforms to the surface of the frame member. A seal member is disposed in the groove of the drip pan to sealingly engaging the surface of the frame member against fluid leakage therethrough.
In one aspect of the invention, the frame member also has spaced apart slots opening inwardly to an opening defined by the frame member. The drip pan has a plurality of resilient members resiliently engaging the slots to detachably secure the drip pan to the frame member. These resilient members provide a quick and convenient way to install or remove the drip pan without using any hand or power tools.
In another aspect of the invention, the drip pan includes a plurality of access openings to provide ready access to mechanical linkages and fluid level indicators. Removable access covers have peripheral seal members which sealingly engaged the access openings against fluid leakage therethrough. The access covers include resilient members which resiliently engage grooves located in the access openings. These resilient members provide a quick and convenient way to install or remove the access covers without using any hand or power tools.
In still another aspect of the invention, the opening defined by the frame member is transversely disposed or shifted to one side of the frame member. As a result the four frame rails forming the frame member have varying widths. The shift of the opening provides improved access to an oil filter on particular helicopters. To provide even further access, a specific corner section of the frame member is machined or milled down so that the oil filter can be removed along a line not perpendicular to the drip pan.
The drip pan apparatus of the present invention maintains its sealing integrity more effectively than prior drip pan apparatuses. Specifically, the peripherally located seal member continues to sealingly engage the surface of the frame member even when the structural opening and the frame member flexes out of the plane of the drip pan apparatus.